This shot of meadowsweet (Spirea latifolia) was taken between 7:30 and 8:00 AM. As you can see, someone fell asleep in the flower.
Spotted knapweed (Centaurea maculosa) is considered an invasive. Most of our roadside plants are not native, and it is easy to see how they spread, thanks to all the traffic along our roadways. I have a couple varieties of Centaurea in my gardens at home, and I can attest to the fact that they are "vigorous growers" and they spread like wildfire.
White sweet clover (Melilotus alba) is one of my favorite roadside plants. There's just something about the slender spires that appeals to me.
I've always called these yellow flowers evening primroses, but true evening primroses open in the evening (big surprise there). Nope, if you see an "evening primrose" open during the day, it is most likely a sundrop (Oenothera fruticosa).
Asters are notoriously difficult to key out. I did not have my field guide with me when I took this, and there's not enough of the plant in the photo for keying. Based on what little I can see, this could be cornel-leaved aster (Aster infirmus). The flowers are too big (I think) for flat-topped aster (Aster umbellatus), definitely too big for small white aster (A. vimineus), and too dense for upland white aster (A. ptarmicoides), although the latter does grow in limestone areas, which describes Newcomb fairly well.
Another of my roadside favorites is birdsfoot trefoil (Lotus corniculatus). When I was a kid, my favorite crayon was "Lemon Yellow," and this non-native flower is the embodiment of that color. Even on grey days its bright yellow sings out...sunshine incarnate. And wandering around this specimen we have a mystery ladybug. I'll be sending its photo into the Lost Ladybug Project for ID.